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OTTA SEAL TRIALS IN KWAZULU-NATAL, SOUTH AFRICA

OTTA SEAL TRIALS IN KWAZULU-NATAL, SOUTH AFRICA. by S. Oloo , D. Thevadasan and H. Bennett. Outline. Introduction Location of test site Characteristics of trial section Performance of trial section Conclusions. Introduction. Where is KwaZulu Natal?. Introduction. Road Network

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OTTA SEAL TRIALS IN KWAZULU-NATAL, SOUTH AFRICA

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  1. OTTA SEAL TRIALS IN KWAZULU-NATAL, SOUTH AFRICA byS. Oloo, D. Thevadasan and H. Bennett

  2. Outline • Introduction • Location of test site • Characteristics of trial section • Performance of trial section • Conclusions

  3. Introduction • Where is KwaZulu Natal?

  4. Introduction • Road Network • Total 23 000 km, Gravel 17 000 km (74%) • Problem • Shortage of gravel • Accelerated gravel loss • Long haul distances (> 30 km) • Solutions • Blacktop even under low traffic • Seals too expensive • Consider Otta seal

  5. Location of test site Bothas Hill Drummond Hillcrest Everton

  6. Characteristics of trial sections • Pavement • Trial Sections: • 11 No., 8 discussed • Combinations of aggregate, prime, anti-stripping agent Otta seal 150mm decomposed granite 150mm Road Bond treated decomposed granite

  7. Section 1 2 3 4 5 6 7 8 Aggregate Anti-Stripping agent Prime Aggregate Wetting agent Prime Crushed stone None None Natural gravel 0.8% by weight MC30 Characteristics of test site

  8. Characteristics of test site • Aggregates • Crushed quartzite & Decomposed granite • Binder • 150/200 pen. Bitumen, 1.6 – 1.9 l/m2 spray rate, 8 – 11% paraffin cut back • Prime: MC 30 • Anti-stripping agent: duominic-T, 0.8% by mass

  9. Quartzite stone

  10. Decomposed granite

  11. Performance of trial sections • One week after • Large quantities of loose stone on surface • Binder barely visible • No difference between sections

  12. Performance of trial sections • One month after • Binder visible following brooming • Curing advancing well • Higher binder content section showing signs of bleeding • Rutting & corrugations in some sections

  13. Performance of trial sections • Two months after • Binder moved to surface • Higher spray rate sections bleeding • Potholes in crushed rock sections

  14. Performance of trial sections • Six months after • Curing complete • Uniform dark premix-like surface • Bleeding serious on gravel sections • Severity of potholing increased

  15. Conclusions • The performance of both aggregates unsatisfactory partly due to grading being outside recommended envelope. • Binder application rates and amount of cutback appear to influence the performance of the Otta seal. • Priming did not influence performance. • Rutting and corrugations can occur as a result of Otta seals following the contour of the base. Proper finishing required. • Generally Otta seal has potential.

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